Passive Vs Active house; which is more ideal? How different are they? At a glance, they do not appear dissimilar.

However, there are key divergences regarding energy efficiency and comfort, influencing many other aspects of a building’s use. These standards also hold sway over the application of bio-based materials in construction. The passive house approach is immensely effective in achieving and surpassing insulation recommendations for reducing carbon emissions, which adheres to government recommendations based on mounting climate concerns. However, such proposals do not consider the lived experience of a building. Such high standards of airtightness also negatively impact the application of bio- based materials, as their more permeable nature means they struggle to obtain passive house certification, unlike conventionally insulated buildings. Active house’s greater attention to comfort allows more leeway around airtightness and, in conjunction, bio based materials.

Misguided National Energy Policies

Government decarbonisation goals primarily promote an electricity-based approach. However, the costs of this method should be addressed in current construction debates. Centring decarbonisation around electricity obstructs the route to achieving sustainable and desirable homes. It runs the risk of deterring building residents from environmentally conscious decisions and acts as a plaster over more significant issues of building composition.

Heat Recovery Systems

One way this occurs is through the frenzied adoption of renewable energy systems. A prime example is air source heat pump (ASHP). These systems transfer heat from the outside air to indoors and offer a renewable alternative to conventional gas and oil-powered heating systems. While effective when properly installed, ASHPs require electricity to run, and their functionality is influenced by a building’s level of air tightness. The importance of high insulation is a trope that needs to be edited in the context of construction. 

ASHP: Further Costs

• Installation: on average £7000 – £18000, prices unfeasible for many UK residents
• Colder temperatures incur higher costs.
• Resizing of radiators on ASHP circuits
• Offer short-term solutions to issues that have deep roots in a building’s structural integrity, which risk worsening in the background until a heat pump ceases to function effectively.

The Pendleton Problem

Efforts to reduce carbon emissions have also seen the clumsy introduction of heat recovery systems in housing projects. Heat recovery systems often involve combinations of different approaches. These solutions take up more space than ASHPs. A typical example was a project in Pendleton’s social housing scheme in Salford. This scheme involved the installation of massive heat recovery systems into small apartment kitchens, taking up almost half of the space. These systems sapped so much energy that most were turned off to reduce exorbitant electricity bills. 

Plastic Bag Approach

Aiming to avoid disasters like that at Pendleton, passive house standards might be turned to as a solution. Passive house measures are strict and often deliver on design checklists. The passive house method favours the installation of highly airtight insulation in large quantities and ASHPs. Although this effectively reduces a building’s carbon emissions and aligns with government decarbonisation goals, it also encourages a building’s dependence on electricity. Airtightness not only adds to electrical reliance but also increases the chances of human respiratory issues, as dust particles and air pollutants remain trapped. It could be that mechanical airtightness with system connections, in the future, answers these crucial issues, strengthening passive house credentials.

Redirecting Building Standards

This piece aims to accentuate the significance of breathability and the nature of materials in building structures when creating both environmentally friendly and comfortable homes. 

Imagine the perfect building as a body. It should function freely or with minor electricity aid to maintain desirable heat and humidity levels. Reliance on electricity combined with airtightness merely places a large plaster over deep-rooted structural issues. There are alternative standards that encourage more balance between airtightness and comfort, such as active house. This standard was developed from the Trias Energetica model, developed by Delft University of Technology, which states:

‘Only when a building has been designed to minimise energy loss, then after should the focus shift to renewable energy solutions and recovery systems.’

Similarly to the passive house, the active house model has been influenced by current global aims to harness renewable energy systems and airtightness in construction. However, active house standards are more geared towards inhabitant comfort. For this reason, building to active house standards will allow for an overall healthier design environmentally and for inhabitants. 

Further Sources

• Heat Recovery Systems – Advantages and Disadvantages
• Air source heat pumps and their role in the Swedish energy system
• Active House Guide
• Passive House
• Heating up the global heat pump market
• Airtight new homes creating serious health problems
• Evidence of poor ventilation in 200-home study
• A rapid review of the impact of increasing airtightness on indoor air quality

Find out more about our breathable insulation.